I do a lot of drilling into plate stainless steel, and as you can probably imagine, this destroys a lot of bits. Typical Chinese HSS bits are good for 2-3 holes before they become dull, and or overheat and detonate. These comoware cobalt bits last 30-50 holes, which is to say, a huge improvement.

I bought these to drill some small holes in (very) hardened steel about 1/8 inch thick. Would not do anything. These are cobalt coated and I'm sure with use the coating will wear off. Again, I was working with extremely hardened steel so I'll give these another chance.

**UPDATE**
Well unfortunately I have to amend my review after using these bits a little more and especially after my last experience with them. At first I thought they were decent quality for the price. I wasn't expecting the performance or durability of a $200 set but they are supposed to be cobalt after all which you buy to drill steel and should outperform everything else except some carbide or diamond bits. These didn't outperform Ryobi black oxide but less HSS bits am I'm questioning if these are actually cobalt bits after what just happened. I was drilling a piece of about 1/8" galvanized steel with the brand new 3/16 bit from this set while using generous amount of cutting wax and not only did it not drill through the steel but it completely burned up to the point that it's ruined (see pics). Cobalt should excel in high heat so like I said these turned out to be a waste of money. Buy a good set of HSS bits, use them correctly and they'll serve you better and longer than 20 sets of these.

To my comrades that complained or left negative reviews about these bits; going off what most of you wrote you misused these bits therefore causing them to break or fail some other way which isn't the bits fault. Cobalt bits are not general purpose bits and should not be used as such. They are for drilling hard metals like stainless, cast, etc. These metals are hard which require a bit made of even harder metal. This is where cobalt bits come in. If you don't know the basics of metallurgy or 6th grade science, the harder metal gets the more brittle it is. If you drop them, bend, or torque them they will snap. So if you're some diy'r buying these to do work around the house you're probably gonna break them then come on here and complain about how they broke the first time you used them for hanging a flower pot or a sign on your wall that says something like "Mr Right, Ms Always Right" or something else but equally deplorable. If you do need to drill hard steel I would stick with the M35. I would only recommend M42 bits if you're using a drill press as they are too brittle for putting into a cordless drill and trying to freehand some straight holes. Also always remember to use cutting wax or fluid, it will drastically prolong the life of your bits. So are these top quality bits that are going to last you a long time that you're gonna take to get sharpened? No, but for the price they are an excellent value and when used properly should give you many holes!

I had a little project at home which required drilling a couple holes in a solid stainless steel bar 7/8 inch in diameter. This was the first time I needed to do this. I bought the 15 piece version of this tool set. The holes needed to be bigger than 1/8", so I chose the the 9/64" drill bit. I didn't have a drill press and vice to hold the bar in place, so I just used my foot to pin the bar up against the inside corner of my garage's concrete step. That worked well. I added a little cutting oil to the outside of the bar. And I started drilling with my cheap 7 amp hand drill.

After a few seconds, I saw it was working. I added more oil and pressed more firmly. I got pretty far into the bar before the drill bit snapped in half. Oops. So I grabbed the next drill bit up in size, the 5/32" bit. This worked fine. I got through the bar twice to make two holes with that drill bit, using cutting oil as I went. It took about 5 minutes to get the hole completely through the bar. Not bad!

I was impressed at how easy it was. There were no sparks, but the drill bit did get hot. Yes, that first drill bit did break. But that probably means I was leaning on the drill a bit too hard or was using too high a speed on the drill. I don't blame the drill bit. The other drill bit that didn't break still looks as good as new. No noticeable wear. I thought it would be a single use only, but it looks fine. And that was indeed a solid steel bar (316 stainless).

Before I did this, I watched a short video on Youtube about how to properly drill into steel. The video emphasized the importance of not using the highest speed on your drill. If you use the highest speed, it will just create too much heat, and the drill bit can snap. You do want to lean into it and put pressure on it. So it should feel slow/medium in speed, but with a good amount of pressure. The metal that comes off of the thing you're drilling into should look like spaghetti: long strands of metal. If the metal is coming off in flakes or powder, you're probably going too fast or not putting enough pressure on it.

Glad I didn't have to invest in a drill press, vice, and workbench. I might need those someday, but so far I've done without them. And my garage is already too cluttered with other junk. :)

Hope that helps.

Needed these to drill some sheet metal. Used a DeWalt drill and some force. Needed to make a pilot hole first, then a larger hole. Both worked good. Good packaging and quick delivery